Semiconductor transistors, in particular field-effect controlled switching devices such as a Junction Field Effect Transistor (JFET), a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) and an Insulated Gate Bipolar Transistor (IGBT) have been used for various applications including but not limited to use as switches in power supplies and power converters, electric cars, air-conditioners, and even stereo systems. Particularly with regard to switch-mode power supplies, power transistors capable of switching large currents and/or operating at higher voltages and having a particularly low power loss are often desired. During operation of a switch-mode power supply, a body diode formed between a body region and a drift region of the Field-Effect Transistor (FET) may be switched in forward direction. In this operational status a loss occurs which depends on the forward voltage drop of the body diode. Furthermore, depleting the drift region during switching the FET results in switching losses. The switching losses increase with increasing operating frequency which is often desired to reduce weight and size of the switch-mode power supply.
An external or integrated Schottky diode may be used as a so-called free-wheeling diode to reduce switching losses. However, external Schottky diodes require external wirings resulting in additional inductivities. Integrated Schottky diodes typically require additional wafer space and/or a more complex processing. This may result in higher costs.
Accordingly, there is a need to improve field-effect semiconductor transistors.